ill tell u what i did.. to begin with had an complete backup of the leopard installation using time machine..

~installed the latest quick time (downloaded from the apple website) ,
~replaced all the files in ~/library/quicktime with the ones from before the installation.
~garageband which was reporting it needs a latest version of QT to start .started all rite!!

solved the issue for me .. not sure if the main files which are updated themselves are being replaced ...